The present invention relates to an alignment technique for assembling collimator modules.
In the radiography apparatus, as represented by an X-ray CT apparatus or a general imaging apparatus, a collimator unit placed on the detecting surface side of a radiation detector is highly important for preventing degradation of images due to scattered radiation.
Conventionally, a collimator unit has a plurality of collimator plates arrayed in one direction. In recent years, because of rising demand of increasing the number of row-detectors, miniaturization and image quality enhancement in the radiation detecting device, a collimator unit having a plurality of collimator plates assembled in lattice-shape for preventing two-dimensionally the scattered radiation entering the detection surface, is proposed. For example, FIGS. 1-7 of JP Unexamined Patent Application No. 2010-127630 disclose such a lattice-shaped collimator unit.
Also, another type of the lattice-shaped collimator unit can be considered as below. For example, a lattice-shaped collimator unit includes a plurality of collimator modules. Each of the plurality of collimator modules includes a plurality of first collimator plates arrayed in a first direction, and a plurality of second collimator plates arrayed in a second direction orthogonal to the first direction. Each of the plurality of first collimator plates has multiple slots (long and thin holes) on the plate surface, and each of the plurality of second collimator plates is inserted into the slots.
When assembling the above type of collimator unit, in order to insert the second collimator plate smoothly into the slot and place it without bending it, the plurality of first collimator plates is required to be positioned precisely in the second direction.
Actually, however, a collimator module or a collimator unit has an enormous number of collimator plates, for example, ranging from several dozens to several hundreds. That makes it difficult to place all collimator plates at correct positions in a precise manner and at low cost.
For example, assuming that a collimator unit of the above type is manufactured, the plurality of first collimator plates is supported by two end-blocks having respective grooves for positioning each edge of the first collimator plate in the second direction.
In this case, a bottom surface of the groove of the end-block is processed as a reference surface, and the position of the first collimator plate may be aligned by contacting the edge portion of the first collimator to the reference surface. However, even under the present technology, it is difficult to process each groove with required high precision, which worsens yields and increases manufacturing cost.
Under such circumstances, low-cost and high precision collimator modules are demanded.